Can Wet Aggregate Stability and Texture Regulate Organic Carbon Stock in Alluvial Soils of East Champaran (Bihar)?

Aims: Here in this experiment, the investigation was done for the relationship among the various soil health parameters i.e., soil organic carbon (SOC), soil texture, and wet aggregate stability (WAS). Place and Duration of Study: Sample: Collection of soil samples were done from 0-15 cm depth from East Champaran is situated in Bihar and is located at 26038’N and 84054’E in the year 2019-2020. Methodology: Soil texture: 14g (+/- 0.1g) of sieved soil was added to a 50 ml centrifuge tube holding 42 ml of a dispersant 3% sodium hexametaphosphate solution follwed by 2 hr shaking and 0.053 mm sieved. Water stable aggregates: Each 0.25-mm sieve contained 4g of air-dried, 2-mm aggregate soil. Each sample's precise weight was recorded. The soil samples were dispersed for 3 minutes with 100 mL distilled water and then for 10 minutes with a 2 g/L sodium hexametaphosphate solution. Pre-weighed filter sheets were used to filter both solutions. Each filter paper was weighed after being oven-dried at 105°C. Soil organic carbon: The amount of soil organic carbon (SOC) was calculated using the Walkley and Black technique (1934). Results: Wet aggregate stability and soil organic carbon storage were shown to have a strong positive connection. Soil carbon stock in soils of East Champaran varied between 5.27-19.60 Mg ha-1 with an average of 12.98 Mg ha-1. WAS ranged from 3.82 to 36.43% with a mean of 16.11%. The results revealed that WAS increased with increase in SOC stock. This experiment also revealed that clay (%) and silt (%) directly affect WAS and hence enhance SOC storage. Conclusion: So, it can be concluded that WAS and soil texture directly and positively impact SOC storage in soils of East Champaran, Bihar.

Selection of an Appropriate Depressant in Flotation Separation of Molybdenum Oxide from Fluorapatite

The depressive efficiency of sodium silicate, sodium hexametaphosphate, and tartaric acid on the flotation separation of molybdenum oxide from fluorapatite were examined using cetylpyridinium chloride (CPC) as the collector. The corresponding depression mechanisms of all three depressants were studied with the use of laboratory measurements. Individual mineral flotation tests and adsorption studies showed that all these depressants have a higher depression effect on fluorapatite than molybdenum oxide. Sodium hexametaphosphate has the strongest depression effect on fluorapatite and can reduce the flotation recovery as low as less than 20%. Infrared spectroscopy and zeta potential tests proved the rationality of the flotation results, indicating that when CPC was used as a collector, the effect of sodium hexametaphosphate on the surface of molybdenum oxide was smaller than that on fluorapatite. The adsorption of hexametaphosphate on the surface of fluorapatite was determined to be physical adsorption.

Synthesis of L-asparagine Catalyzed by a Novel Asparagine Synthase Coupled With an ATP Regeneration System

Compared with low-yield extraction from plants and environmentally unfriendly chemical synthesis, biocatalysis by asparagine synthetase (AS) for preparation of L-asparagine (L-Asn) has become a potential synthetic method. However, low enzyme activity of AS and high cost of ATP in this reaction restricts the large-scale preparation of L-Asn by biocatalysis. In this study, gene mining strategy was used to search for novel AS with high enzyme activity by expressing them in Escherichia coli BL21 (DE3) or Bacillus subtilis WB600. The obtained LsaAS-A was determined for its enzymatic properties and used for subsequent preparation of L-Asn. In order to reduce the use of ATP, a class III polyphosphate kinase 2 from Deinococcus ficus (DfiPPK2-Ⅲ) was cloned and expressed in E. coli BL21 (DE3), Rosetta (DE3) or RosettagamiB (DE3) for ATP regeneration. A coupling reaction system including whole cells expressing LsaAS-A and DfiPPK2-Ⅲ was constructed to prepare L-Asn from L-aspartic acid (L-Asp). Batch catalytic experiments showed that sodium hexametaphosphate (>60 mmol L−1) and L-Asp (>100 mmol L−1) could inhibit the synthesis of L-Asn. Under fed-batch mode, L-Asn yield reached 90.15% with twice feeding of sodium hexametaphosphate. A final concentration of 218.26 mmol L−1 L-Asn with a yield of 64.19% was obtained when L-Asp and sodium hexametaphosphate were fed simultaneously.

Study on regulators of purifying magnesite ore by cationic reverse flotation

The floatability of magnesite, dolomite and quartz is a major factor affecting the removal of silicon and calcium from magnesite ore. The effect of the regulators sodium hexametaphosphate (SH), sodium silicate (SS), trisodium phosphate (TP), tannic acid (TN) and monoammonium oxalate (OA) on the floatability of magnesite, dolomite, and quartz under the ether amine (EAH) system was studied. The results show that the five regulators have relatively little influence on the floatability of quartz and magnesite. Dolomite can be activated when the dosage of SH is less than 40 mg/L; however, dolomite can be inhibited when the SH dosage is greater than 40 mg/L. The other four regulators have inhibitory effects on dolomite, and TN and TP have strong inhibitory effects on dolomite. Under the conditions of optimum grinding fineness, pH and collector dosage, a recovery of approximately 70% and a concentrate with a grade of over 47% were obtained by three stages of reverse flotation using sodium hexametaphosphate and water glass as regulators and Haicheng magnesite ore with an SiO2 content of 2.38% and a CaO content of 0.75%. Potentiometric measurements and infrared spectroscopy analysis show that physical adsorption occurs between the three minerals and collectors, while the interaction of magnesite and dolomite with SH and SS involves both physical adsorption and chemical adsorption.

Chalcopyrite and Molybdenite Flotation in Seawater: The Use of Inorganic Dispersants to Reduce the Depressing Effects of Micas

The objective of this work was to study the effect of muscovite and biotite on the flotation of chalcopyrite and molybdenite in seawater, and the use of sodium hexametaphosphate and sodium silicate to improve copper and molybdenum recoveries. The impact of the inorganic dispersants on the settling properties of the resulting flotation tailings was also studied. It was found that muscovite and biotite depress the flotation of chalcopyrite and molybdenite in seawater, with this depressing effect being stronger at pH 11 than at pH 9. Sodium hexametaphosphate and sodium silicate increased the recoveries of copper and molybdenum in seawater. These dispersants render the mineral particles more negatively charged and remove the hydroxy-complexes of magnesium and calcium from the mineral particles causing dispersion of the slimes. The settling rates of the flotation tailings slightly decrease when sodium hexametaphosphate and sodium silicate were added in the flotation stage. The presence of ultrafine particles dispersed by the action of the inorganic dispersants negatively impacted the flocculation and sedimentation processes leading to high flocculant consumption, low settling rates and high turbidity of the supernatant.